Mobile communication devices are popular for business and personal use. Such devices include Personal Digital Assistants (PDAs), cellular phones and smart phones. These devices provide wireless two-way voice and data communication over wireless networks such as GSM/GPRS, CDPD, TDMA, iDEN Mobitex, DataTAC, EDGE or UMTS networks, and broadband networks like Bluetooth and variants of 802.11.
It is desirable that the electromagnetic fields generated by such devices be minimized for health reasons and in order to reduce interference with other nearby electronic devices. For example, international standards on Hearing Aid Compatibility (HAC) establish a minimum signal-to-noise (SNR) ratio at the T-coil of a hearing aid (for example, see section 7.3.4 “Signal Quality” of ANSI C63.19-2007) for effective magnetic wireless coupling to the hearing aid (including hearing aids, cochlear implants, and assistive listening devices) while minimizing magnetic interference. The hearing aid compatibility requirements are generally evaluated with the hearing aid coil in close proximity to the receiver in the mobile communication device. Traditional approaches to meeting the required signal-to-noise ratio in the presence of magnetic fields generated by mobile communication devices include increasing current in the mobile communication device receiver, installing a separate T-coil within the mobile communication device, and altering current loops and circuit board traces within the mobile communication device to minimize magnetic interference.